Fluorination of Fluoropolymer Resin to Reduce Discoloration
Inactive Publication Date: 2013-11-14
THE CHEMOURS CO FC LLC
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- Abstract
- Description
- Claims
- Application Information
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Benefits of technology
The process described in the patent reduces color distortion caused by heat by at least 10% as measured by a color scale.
Problems solved by technology
However, when fluoropolymer dispersion is formed which contains hydrocarbon surfactant and is subsequently isolated to obtain fluoropolymer resin, the fluoropolymer resin is prone to thermally induced discoloration.
By thermally induced discoloration is meant that undesirable color forms or increases in the fluoropolymer resin upon heating.
For example, if PTFE fine power produced from dispersion containing the hydrocarbon surfactant sodium dodecyl sulfate (SDS) is converted into paste-extruded shapes or films and subsequently sintered, an undesirable gray or brown color will typically arise.
Similarly, when melt processible fluoropolymers such as FEP or PFA are produced from dispersions containing hydrocarbon surfactant such as SDS, undesirable color typically occurs when the fluoropolymer is first melt-processed, for example, when melt processed into a convenient form for subsequent use such as chip or pellet.
Method used
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Examples
Experimental program
Comparison scheme
Effect test
example 1
Exposing Fluoropolymer Resin to Fluorine
[0093]Aqueous FEP dispersion polymerized as described above is coagulated in a heated glass reactor. 1250 ml of dispersion is heated to 85° C. in a water bath and then transferred to a 2,000 ml jacketed glass reactor with four internal baffles produced by Lab Glass or Vineland, N.J. where the temperature is maintained at by circulating 85° C. water through the jacket. Two high-shear impellers are turned at 2,470 rpm for 3600 seconds to cause the dispersion to separate into a polymer phase and a water phase. The water is separated from the solids by filtering through a 150 micron mesh filter bag model NMO150P1SHS manufactured by The Strainrite Companies of Auburn, Me. The polymer phase is dried for 40 hours in a circulating air oven set at 150° C. to produce a dry powder.
[0094]A sample of dried powder is molded to produce color films as described in the Test Methods section above as Measurement of Thermally Induced Discoloration for melt-proces...
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Abstract
Process for reducing thermally induced discoloration of fluoropolymer resin produced by polymerizing fluoromonomer in an aqueous medium to form aqueous fluoropolymer dispersion and isolating said fluoropolymer from said aqueous medium to obtain said fluoropolymer resin. The process comprises:exposing the fluoropolymer resin to fluorine.
Description
FIELD OF THE INVENTION[0001]This invention relates to a process for reducing thermally induced discoloration of fluoropolymer resin.BACKGROUND OF THE INVENTION[0002]A typical process for the aqueous dispersion polymerization of fluorinated monomer to produce fluoropolymer includes feeding fluorinated monomer to a heated reactor containing an aqueous medium and adding a free-radical initiator to commence polymerization. A fluorosurfactant is typically employed to stabilize the fluoropolymer particles formed. After several hours, the feeds are stopped, the reactor is vented and purged with nitrogen, and the raw dispersion in the vessel is transferred to a cooling vessel.[0003]The fluoropolymer formed can be isolated from the dispersion to obtain fluoropolymer resin. For example, polytetrafluoroethylene (PTFE) resin referred to as PTFE fine powder is produced by isolating PTFE resin from PTFE dispersion by coagulating the dispersion to separate PTFE from the aqueous medium and then dry...
Claims
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Patent Timeline
Login to View More IPC IPC(8): C08F8/22
CPCC08F8/22C08F214/262C08F6/22C08F2800/20C08F2810/10B29C48/395B29C48/468B29C48/57B29C48/625B29C48/67B29C48/76C08F14/26C08F2/26C08F2/30C08F6/28C08L27/18C08F214/26C08F214/28C08F216/1408
Inventor BROTHERS, PAUL DOUGLASBURCH, HEIDI ELIZABETHCHAPMAN, GREGORY ALLENGANGAL, SUBHASH VISHNU
Owner THE CHEMOURS CO FC LLC